Bag packer weighing assembly



Aug 4, 1964 E. J. D i-u sLAsl BAG PACKER WEGHING ASSEMBLY Filed. Marchso, v196cv 3 Sheets-Sheet 1 WSNS Aug. 4', 1964 E. J. DOUGLAS 3,143,178

BAG PACKER WEIGHING ASSEMBLY Filed March .'50, 1960 5 Sheets-Sheet 2 INVEN TOR.

Aug. 4, 1954 E. J. DOUGLAS 3,143,178

' BAG PACKER WEIGHING ASSEMBLY Filed March 50, 1960 3 Sheets-Sheet 3 INVEN TOR.

United States Patent O 3,143,178 BAG PACKER WEIGHING ASSEMBLY Edwin J.Douglas, Whittier, Calif., assignor, by mesne assignments, toCherry-Burrell Corporation, Cedar Rapids, Iowa, a corporation ofDelaware Filed Mar. 30, 1960, Ser. No. 18,648 1 Claim. (Cl. 177-420)This invention relates to weighing assemblies for bag packers and thelike. In particular, the invention is concerned with improving theaccuracy and speed with which bags may be packed with material by a highspeed bag packer.

Devices for high speed bag packing, utilizable with a variety ofmaterials, are well-known. An example of such a bag packer isillustrated in my United States Patent No. 2,827,256, issued March 18,1958, and assigned to H. L. Stoker Company, Claremont, California. Thebag packer therein described consists essentially of a U-trough having ahopper attached thereto and holding a screw conveyor. A drive assemblyisprovided to rotate the screw conveyor. Material is fed into the U-troughthrough the hopper and conveyed by the screw conveyor out of the U-trough and into a bag connected to a spout at the end of the conveyor. Aweight sensing device is provided to weigh the material packed in thebag from the u-trough.

A bag packer of my aforesaid patent is capable of packing bags withmaterial at a very high rate while maintaining accuracy in the weight ofmaterial filled in each bag and from bag to bag. That bag packerutilizes a two-speed drive arrangement by means of which the material tobe packed is fed into the bag at a high rate of speed until the bag issubstantially filled, whereupon the rate of packing is very greatlyreduced so as to complete the filling of the bag with a high degree ofaccuracy with respect to the weight of material filled. The weightsensing device senses two weight end points which occur during thefilling of the bag. Control means are actuated at each of the two endpoints successively to reduce the rate of the screw conveyor rotationand then reverse the screw conveyor rotation, so as to provide a sharpcutoff in filling. By providing such a sharp cutoff, a reproducibleaccuracy in filling from bag to bag is accomplished.

However, the bag packer described in the aforesaid patent has thecomparative disadvantage of not maintaining a high constant flow rate ofmaterial throughout the packing cycle. While providing speeds of packingand accuracy of measurement equal or superior to conventional bagpackers, such speed and accuracy is achieved by utilizing a variablerate of flow of material. Therefore, an even greater rate of packing ispossible if the high initial rate of packing can be maintainedthroughout the packing cycle.

Bag packers have conventionally utilized as the primary weighing elementa scale beam connected so as to constitute a lever of the first class.In other words, conventional bag packer weighing assemblies, consistingessentially of a weighing platform adapted to hold a bag, a scale beam,and means for counterbalancing the weight of the material in the bag,have had the weighing platform connected at one end of the scale beamand the counterbalancing means connected at the other end of the beam. Apivot point between the two connections acts as a fulcrum so that thescale beam constitutes a lever of the first class. The movement of thescale beam, as the material packed into the bag and the force exerted bythe counterbalancing means equalize each other, whereupon the scale beamassumes a horizontal position, has been utilized to actuatemicroswitches and relays to terminate packing of the material by the bagpacker screw conveyor. In such conventional bag packers, both the loadapplied to the scale beam by the weighing platform and the force3,l43,l78 Patented Aug. 4, 1964 applied to the scale beam by thecounterbalancing means are applied in a downward direction.

According to the present invention, a weighing assembly is constructedso that the scale beam constitutes a lever of the second class. Theweighing platform applies the load in a downward direction, as inconventional bag packers, but the counterbalancing means applies a forcein an upward direction, whereas previous bag packers applied such aforce in a downward direction. The movement of the scale beam upon thesubstantial counterbalancing of the weighing platform load by thecounterbalancing means is utilized to terminate the packing of the bag.

It is preferred to include a weight beam connected so as to constitute afirst class lever with a weight attached at one end thereof as thecounterbalancing means. The fulcrurn of the weight beam lever ispositioned so that the weight beam amplifies the movement of the scalebeam upon the substantial counterbalancing of the weighing platformload. The amplified motion of the weight beam is then used to terminatethe packing of the bag. For example, a capacity-sensitive electricalcircuit having a variable capacitor, the capacitance of which is variedby movement of the weight beam, may be utilized to terminate the packingof the bag at a predetermined value of capacity of the variablecapacitor.

The invention may be more readily understood by referring to thedrawings in which:

FIGURE 1 is a block diagram of a bag packer weighing and packing controlassembly according to the invention;

FIGURE 2 is an elevation, partially in section, of a bag packeraccording to the invention;

FIGURE 3 is a fragmentary elevation of the bag packer of FIG. 2illustrating the construction of the weighing assembly;

FIGURE 4 is a partial section taken along lines 4 4 of FIG. 2illustrating the means by which the weighing platform is supported fromthe weighing assembly frame; and

FIGURE 5 is a partial view of a scale beam arm of the deviceillustrating the construction of the fulcrum pivot point thereof.

Referring now to FIG. 1, a screw conveyor 11 is contained in a trough(not shown) into which material 12, which is to be packed, is fed. Therotation of the screw conveyor by a screw conveyor drive motor 13 causesthe screw conveyor to transport the material contained in the troughthrough and out of a spout 14 and into a bag 1S.

A weighing platform 16 is adapted to support the bag 15 while the bag isbeing packed with material. The weighing platform 16 is connected to abag weighing device 17 which drives a variable capacitor 18. Thevariable capacitor 18 is connected to a screw conveyor drive controllercircuit 19. A power supply 20 is connected to a bag packer start switch21. The bag packer start switch is operable to apply electrical power tothe contacts of a forward drive relay 22 and a reverse drive relay 23.Completion of an electrical circuit through one of these drive relays22, 23 to the screw conveyor drive motor 13 will cause the screwconveyor drive motor to rotate the screw conveyor 11 in the appropriatedirectoin. The completion of electrical circuits through the driverelays 22 and 23 is controlled by the. screw conveyor drive controller19. A reverse drive timer 24 is connected in series with the screwconveyor drive controller 19 and the reverse drive relay 23 to controlthe duration of the reverse drive of the screw conveyor 11.

The operation of the screw conveyor drive controller 19 is controlled bythe capacitance of the variable capacitor 18. The screw conveyor drivecontroller 19 is normally operable to complete an electrical circuitthrough the forward drive relay 22 so that the conveyor screw 11 isrotated to transport material through and out of the spout 14. However,at a predetermined value of capacity of the variable capacitor 13, thescrew conveyor drive controller 19 breaks the electrical circuit throughthe forward drive relay 22 and actuates the reverse drive timer 24. Thereverse drive timer 24 functions to comf plete an electrical circuitthrough the reverse drive relay 23 for a preselected duration of time,thereby causing the screw conveyor 11 to be driven in the reversedirection for this time duration. The screw conveyor 11 is driven in thereverse direction to provide a sharp cutoff in filling, as is describedin my aforesaid patent.

` A satisfactory reverse drive timer is an Agastat Model 9050 Timer.V Asatisfactory screw conveyor drive controller is a Robertshaw-FultonModel 201 Capacity-sensitive Relay. The Robertshaw-Fulton Model 201relay is preferably connected to the variable capacitor by coaxialcable.

FIGURE 2 shows a bag packer constructed according to the invention. Aweighing platform 30 is connected to a weighing assembly frame 31 bylower straps 32 and upper straps 32', which are more clearly shown inFIGS. 3 and 4. The weighing platform 30 includes a spout 34 connectedintegrally therewith. A screw conveyor (not shown) extends through aU-trough 35 which has a hopper 36 connected thereto.

The construction of the spout 34, U-trough 35 and hopper 36 isillustrated in FIGS. 3 and 4 of my copending Application Serial No.805,397, filed April 10, 1959, and assigned to the H. L. Stoker Company,Claremont, California, using a iexible seal. A drive motor 37 drives theconveyor screw through a removable screw assembly 33 and a Vbelt 39.,The preferable construction of the removable screw assembly 38 isillustrated in my Application Serial No. 831,201, filed August 3, 1959,and assigned to the H. L. Stoker Company, Claremont, California. v Ascale beam 40 is pivoted at one end from the frame 31, as is shown moreclearly in FIG. 3. At the opposite end a weight beam connecting member42 connects the scale beam to one end of a weight beam 43. The weightbeam 43 has a poise weight 44 and a hanger weight 45 attached thereto. Apivot 46 attached to the assembly frame31 supports the weight beam 43and acts as the fulcrum for the weight beam. Thus, Vthe weight beamconstitutes a rst class lever. A rst capacitor plate 47 is attached tothe end of the weight beam 43 adjacent the weights 44 and 45. A secondcapacitor plate 48 is connected tothe assembly frame 31 by an adjustableheight standoff insulator 49 to provide electrical isolation between thecapacitor plate 48 and the frame. Movement ofthe weight beamV `43 in avertical direction will thus' vary the capacitance of the variablecapacitor 18 (FIG. 1) formed by the first and second capacitor plates 47and 48.

The weighing platform 30 is connected to the scale beam 40 by a weighingplatform connecting member 50. A counter poise weight 51 on the weightbeam 43 and a counterpoise 52 on the scale beam provide a means foradjusting the zero position of the assembly. An over/under indicator 53is attached to the end of the scale beam adjacent the capacitor plate 47to provide visual indication of the correctness of the weight ofmaterial iilled.

FIGURE 3 illustrates the detail of the construction of the weighingassembly of the bag packer. A bag seat 60 of the weighing platform 30'is connected to the spout 34 by`afchannel-shaped connecting member 61.The

scale beam 40 is pivoted fromrthe frame 31 by a pivot slot, in which themale pivot knife rides, is thereby achieved. It has been found that theconventional milled slot is unsatisfactory for this pivot. The weighingplatform connecting memberV 50 is connected to the scale beam 40 by apivot 64, and to the weighing platform 30 by a pivot 65.

The weight beam connecting member 42 is connected to the scale beam 40by a pivot 66. The construction of the pivots 64-66 is more fullydescribed in my aforesaid U.S. Patent No. 2,827,256. These pivots havethe advantage of a construction such that the material being packedcannot infiltrate into the pivotal surfaces to impede free pivotingaction. The weight beam connecting member 42 should be vertical. Thescale beam 40 is therefore preferably constructed so that the positionof the pivot 66 may be shifted to insure that the weight beam connectingmember 42 is vertical.

FIGURE 4 illustrates in moreV detail the straps 32 which connect theweighing platform 30 to the assembly frame 31. The straps 32 arepreferably Vconstructed of clock spring steel 1095 rolled to width so asto provide resilient support for the weighing platform and reproduciblerecovery characteristics. The straps 32 are preferably .032 inchesthick. VA Weighing platform support bracket 67 connects the straps 32 tothe weighingl platform 30. l

By positioning the pivot 64 adjacent the pivot 63 and utilizing a longarm for the scale beam 40, and by attaching the weight beam connectingmember 42 adjacent the weight beam pivot 46, a high amplification of thevertical movement of the weighing platform 30 is obtained in the weightbeam 43. Such a high amplification has two principal advantages. First,a relatively small weighing platform movement produces a comparativelygreat movement of the first capacitor plate 46, thereby` providing agreat variation in the capacitance of the variable capacitor.comparatively light with respect to the weight of material in the bagbeing counterbalanced. Conventional systems require a comparativelyheavy weight for such counterbalancing. Precise measurement of theweight of material in the bag requires that the weight beam movementhave no appreciable time delay with respect to the actual Weight ofmaterial in the bag. Movement of the weight beam also moves the hangerWeight. A heavier hanger weight, in addition to providing as acounterbalancing force its own weight, adds as an additionalcounterbalancing force its inertia, which tends to prevent the movementof the weight beam. By the present invention, an eX- tremcly lighthanger weight is utilized and the inertia thereby introduced isnegligible, so that no appreciableV time delay due to the temporarycounterbalancing force of the balance weight inertia is introduced.

Figure 5 illustrates in detail the construction of the female pivot slotof the pivot 63 described with respect to FIG. 3. A 'slot is cut in thepivot block 70 so as to present a first face 71 and a second face 72,each at an angleof 60 to the block face 73. Ground tungsten carbidechips 74, ground preferably to parallelism, are placed in alternateorder on faces 71 and 72 of the block 7 0. The chips '74 are held inplace preferably by a maten rial such as an epoxy resin. A practicalconstruction of the scale beam rovides for the load pivot point, that pis, the point at which the pivot 64 is positioned, to be placed twoinches from the pivotY pointof the f ulcrum pivot 63 and the force pivotpoint, that 1s, the point at which the load beam connecting member 42 isconnected to the scale beam 40, be thirty inches` from the pivot pointof the fulcrum pivot 63. The loadbeam connecting member is attached tothe load beam three and one-quarter inches from the pivot point of theload beam support 46. The hanger weight 45 is attached to the load beamtwenty-one and ve-eighths inches fromA the pivot point of the loadl beamsupportr46. The first capacitor plate 47 is connected to the load beamtwenty- Second, the hanger weight 4S isV six inches from the load beamsupport 46 pivot point. A hanger weight of one pound is then used tocounterbalance one hundred pounds of material packed into the bag.

Using these dimensions, a downward vertical movement of .0025 inch bythe weighing platform where the system is in balance results in thefirst capacitor plate 47 moving a sufiicient amount to actuate thecircuit to give a cutolf. This high amplification in movement of overone hundred times, insures a rapid change in capacity of the variablecapacitor. The rapid change in capacity provides a reproducibleactuation point for the reverse drive of the screw conveyor. By usingthe reverse drive timer, the reverse rotation of the screw conveyor isalso accurately controlled so that reproducible results are obtained inpacking bags. The exact instant for terminating packing may be adjustedby raising or lowering the standoff insulator 49. Using the abovedescribed system and dimensions, bags can be packed with one hundredpounds of material with a reproducible accuracy of within one ounce. Inorder to maintain such reproducible accuracy, it is essential that thestrength of the components in the device be sufficient to precludedeformations due to loading other than movement of the weighing leverassembly and support straps.

I claim:

A weighing assembly for a bag packer comprising a weighing platformincluding a bag seat and a filling spout adapted to support a bag beingfilled with material, a weighing assembly frame, at least one resilienthorizontal connecting member attached to the weighing platform and theweighing assembly frame so as to support the weighing platform andsimultaneously permit the vertical movement of the bag support assemblyin response to the weight of the material contained in the bag, said oneconnecting member comprising a pair of resilient suspension straps thatare connected to the Weighing assembly frame and extend from oppositesides of the frame in substantially parallel directions in asubstantially horizontal plane, a weighing platform support bracketconnected between the ends of said suspension straps, means forconnecting said weighing platform to said support bracket, a firstpivotal support means that is fixed relative to the weighing assemblyframe, a first substantially horizontal beam pivotally supported at oneend by said first pivotal support means, a second substantiallyhorizontal beam, a vertical beam connecting member connecting one end ofthe second beam to the end of the first beam not pivotally supported,means for attaching a weight to the end of the second beam not connectedto the first beam by the vertical connecting member, a second pivotalsupport means that is fixed relative to weighing assembly frame, saidsecond pivotal support means supporting the second beam at a pointbetween the weight and the connecting member, a vertical weighingplatform connecting member connecting the weighing platform to the firstbeam at a point intermediate between the first pivotal support means andthe vertical beam connecting member, and means associated with thesecond beam to terminate the filling of the bag in response to apredetermined amount of movement of the second beam.

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